Somatic hybridization between the diploids of S. × michoacanum and S. tuberosum

Abstract

Interspecific somatic hybrids between a diploid potato clone DG 81-68 susceptible to Phytophthora infestans (Mont.) de Bary and a resistant diploid tuber-bearing species Solanum 9 michoacanum were generated and analyzed. About 30 regenerants displaying an intermediate morphology were obtained as a result of three separate PEG-mediated fusion experiments. The RAPD analysis confirmed the hybridity of all the regenerants. About 50% of the hybrid plants exhibited vigorous growth and were stable in culture, while the rest of them rooted poorly and grew slowly in vitro. Most of the hybrid clones were at the tetraploid level (70%), while 30% of the clones examined were at the hexaploid level. The S. 9 michoacanum (?) DG 81-68 hybrids with growth anomalies were aneuploid. The variation in late blight resistance of the hybrid clones was found in detached leaflet tests, with enhanced resistance characteristic for three tetraploid hybrids.

Genetic composition of interspecific potato somatic hybrids and autofused 4x plants evaluated by DArT and cytoplasmic DNA markers

“…In susceptible forms predominantly noted in our studies, the expression of a resistance gene might have been silenced. The lack of resistant somatic hybrids or the low frequency of the expected level of resistance to late blight in the somatic hybrid genome were previously noted (Thieme et al 1997; Rasmussen et al 1998; Bidani et al 2007; Szczerbakowa et al 2010; Polzerová et al 2011). Such phenomena could be explained by a ‘dilution effect of non-resistance genes’, which means that expression of a resistant gene from one parental form in somatic hybrids genome is reduced by the presence of non-resistance genes from the other component of the somatic fusion or as a different genome-dosage; chromosomal instability; preferential elimination of some chromosomes; somaclonal variation in an early stage of regeneration, which generated gene mutations in the nuclear and cytoplasmic DNA; translocations and deletions (Thieme et al 1997; Rasmussen et al 1998).…”

“…Of this group, only few hybrids between tbr and Solanum bulbocastanum (Helgeson et al 1998), Solanum nigrum (Horsman et al 2001), Solanum tarnii (Thieme et al 2008), Solanum commersonii (Carputo et al 2000), and Solanum cardiophyllum (Thieme et al 2010) were subsequently backcrossed sexually to potato cultivars and exploited in potato breeding programs. Low number of hybrids suitable for an application in the breeding process have been caused by the low frequency of somatic hybrids maintaining resistance of the donor component, their reduced fertility, crossing incapability or poor tuber performance (Orczyk et al 2003; Szczerbakowa et al 2010). …”

A resistance gene against potato late blight originating from Solanum × michoacanum maps to potato chromosome VII

“…The only documented effort to overcome the crossing barrier between S. michoacanum and S. tuberosum was through somatic hybridization, which resulted in obtaining several hybrids, three of them with enhanced late blight resistance (Szczerbakowa et al 2010). Apart from the late blight resistance, clones that are suitable for the potato crisps production (Jakuczun and Wasilewicz-Flis 2004b) and resistant to the green peach aphid were also found within S. michoacanum (Radcliffe et al 1974).…”

Production and characterization of somatic hybrids between Solanum tuberosum L. and S. pinnatisectum Dun.

“…Numerous experiments had succeeded in the production of potato somatic hybrids by introgression of desirable agronomic and disease resistance traits. In recent years, wild potato species S. pinnatisectum (Greplová et al 2008;Polzerová et al 2011), S. cardiophyllum (Thieme et al 2010), S. 9 michoacanum (Szczerbakowa et al 2010), S. bulbocastanum (Greplová et al 2008) and S. tarnii (Thieme et al 2008) were used to transfer late blight resistance into cultivated potato through somatic hybridization. Protoplast fusion has also been succeeded in other crops like citrus (Grosser and Gmitter 2011), cotton (Sun et al 2011), sweet potato (Yang et al 2009), Brassicaceae (Ovcharenko et al 2011).…”